1. Field of the Invention
The present invention relates to a component-embedded board fabrication method for fabricating a component-embedded board with electronic components embedded in a wiring board, and an apparatus using the same.
2. Description of the Related Art
With the increasing miniaturization and complexity of wiring patterns formed on printed circuit boards, a need is increasing for high-precision wiring forming technologies. On the other hand, as electronic apparatuses shrink in size and increase in performance, multilayered wiring boards are increasingly used. In some wiring boards (hereinafter called “component-embedded boards”), various kinds of electronic components, such as IC chips, semiconductor devices, capacitors, resistors, etc., are embedded, or electronic components such as capacitors, resistors, inductors, etc. are fabricated in integral fashion in the board.
In the case of a single-layered component-embedded board, various electronic components must be arranged in two dimensions, but in the case of a multilayered component-embedded board, electronic components can be arranged efficiently in three dimensions by placing one layer of components above another layer of components. As the wiring length can be reduced compared with the case of a single-layer board, the multilayered structure can achieve a wiring board that is resistant to noise and stray capacitance and that can be used in high-frequency applications.
Generally, a wiring board is fabricated by exposing the board in a desired pattern based on wiring pattern design data, and by developing the desired pattern to print the pattern on it, followed by etching.
Specifically, when fabricating a multilayered component-embedded board, high precision is particularly demanded in the formation of wiring on the multilayered board because not only is the formation of electronic components and the physical formation of multiple layers consisting of insulating layers and wiring layers required, but the interconnection wiring between the wiring layers is also required.
For example, in conventional photolithography using a photomask, when forming an electronic component in a certain layer, the electronic component must be formed by precisely positioning it with respect to the board; otherwise, the via and wiring formed in the subsequent exposure process would be displaced from the connecting terminal of the electronic component.
FIG. 19 is a diagram illustrating the patterning and the resulting positional displacement in a prior art example using a photomask.
In the patterning of the prior art example using a photomask, the mask position and the mask pattern are decided based on design data. However, when forming an electronic component, if the electronic component is not formed by precisely positioning it with respect to the board, an angular displacement θ and horizontal displacements Δx and Δy occur between the mask position and the position where the electronic component is formed.
FIG. 20 is a diagram illustrating the positional relationship between the electronic component and a wiring line projected on the component-embedded board through the photomask. In FIG. 20, the design position 101 of the connecting terminal of the electronic component, that is, the position where the connecting terminal of the electronic component should normally be located, is indicated by a dashed line.
If the electronic component was actually formed in the position indicated by a solid line 102 and was thus displaced from the design position on the wiring board and if the wiring line 103 is formed in accordance with the prior art exposure process using a photomask, a positional displacement would occur between the wiring line and the electronic component.
One possible way to avoid such a positional displacement would be to form the electronic component as faithfully to the design data as possible, but it would be extremely costly to implement such a high-precision fabrication process.
Furthermore, once the board with the electronic component formed thereon is covered with an insulating layer, it is difficult to locate the position of the electronic component. Accordingly, even if a displacement or distortion is caused in the formation of the electronic component, the subsequent processes have to be performed in accordance with the design data, eventually ending up in the production of a defective part.
As described, in the prior art, it is difficult to locate the position of the electronic component once it is covered with an insulating layer; as a result, with increasing number of layers in the board and with increasing miniaturization of the wiring pattern, it becomes increasingly difficult to fabricate a defect-free circuit board.
In view of the above problem, it is an object of the present invention to provide a component-embedded board fabrication method for high-precision and easy fabrication of a component-embedded board with electronic components embedded in a wiring board, and an apparatus for the same.